rootid_from_xattr(9)

💅 rootid_from_xattr(9) — the kernel API manual, but make it make sense 🎀

okay bestie, so this page is called rootid_from_xattr(9) and it lives in the Kernel API Manual section of the kernel docs. We're translating the root uid of vfs caps. That's the whole vibe. Let's get into it ✨

🌸 SYNOPSIS 🌸

vfsuid_t rootid_from_xattr (const void *value , size_t size , struct
       user_namespace *task_ns );

Like, that's the whole signature. Three args, one return type (vfsuid_t), no notes. She's giving "small but mighty" 🔥

🦋 ARGUMENTS 🦋

• value — the vfs caps value, bestie 💖 and heads up: this one may be modified by this function — yes, fr fr, she might touch your data, so don't come crying if it comes back different 😭
• size — the size of ivalue (yes, the page literally says ivalue and I'm not gonna pretend otherwise, we keep the text exactly as it is, no cap 🙈)
• task_ns — the user namespace of the caller, aka whose struct user_namespace * we're working with 👑

🔥 SEE ALSO 🔥

Big list incoming, and honestly? It's giving family reunion 💀 Here's everyone in the Kernel file ./security/commoncap.c crew:

• cap_capable_helper(9)
• cap_capable(9)
• cap_settime(9)
• cap_ptrace_access_check(9)
• cap_ptrace_traceme(9)
• cap_capget(9)
• cap_capset(9)
• cap_inode_need_killpriv(9)
• cap_inode_killpriv(9)
• kuid_root_in_ns(9)
• cap_convert_nscap(9)
• get_vfs_caps_from_disk(9)
• cap_bprm_creds_from_file(9)
• cap_inode_setxattr(9)
• cap_inode_removexattr(9)
• cap_task_fix_setuid(9)
• cap_task_setscheduler(9)
• cap_task_setioprio(9)
• cap_task_setnice(9)
• cap_task_prctl(9)
• cap_vm_enough_memory(9)
• cap_mmap_addr(9)

that's twenty-two (22) references, i counted, and every single one of them is on this page for a reason 🫶 go read them, iykyk 💜

ngl the whole capability subsystem is literally main character energy — this page is just one little xattr girlie in a massive cast 🌈

⭐ the cute little sign-off ⭐

this absolute icon of a page lives under ./security in the kernel tree, and the version we're reading is dated October 2026 🗓️✨ that's the whole footer, bestie — rootid_from_xattr(9) from the ./security corner of things, October 2026, slay 💅🎀